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Help selecting hardware for cutting to lenght application

02-07-2019, 05:01 PM

Hello,
I'm hoping to get some help selecting the correct PLC and encoder for my application. we measure the rotation of a rubber roll pulling plastic sheet, so we can control a shear to cut the sheet at determined preset lenght.
we have an encoder mounted on a shaft. it is slow speed, about 20 rpm typical, but resolution is important, so the encodr needs 1000 pulses per minute at least. direction is not important, as it is always turning 1 way, so quadrature is not important unless it is used to increase the resolution.
the signal to the shear is a simple 110v switch relay.
the operator needs to be able to set the preset value, and a display should display the current value (in linear inches, so actually the pulses need to be scaled), the preset value, as well as the rate of production (feet per minute ) and intervals (time between reacahing presets).

we have always used a durant 5882 controller with their encoder for this task, but although these are very reliable and simple to use, they have been discontinued for years, and it is getting harder to find them...
any help would be greatly appreciated! thank you in advance,
Alex

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thank you RogerR for the input,
I misspoke: I meant our current encoder do 1000 pulses per REVOLUTION, not per minute. the encoder will do typically 10 rpm (I wrote 20, but that's actually very unlikely. typical is 10rpm). so 10'000 pulses per minute, typically. does that mean that I should definitely go with the DoMore?
thanks again,
Alex

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Personally I'd use a Do-More (probably BRX for your application) for most any new application, unless absolutely cheapest was needed in which case I'd use a CLICK but considering that you are presumably going to need some sort of operator interface to set the length, this is not really a dirt cheap project so I'd avoid the CLICK. However, the Ethernet model CLICKs seem to have 100KHz counters so they'd be plenty fast.

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click, Do-More, or the productivity 2000/3000 would all be plenty fast. if I recall correctly they are working on high speed counter card for the productivity 1000 but i don't think they are out as of now.

Do you have any PLC programming experience? I am at a mixed plant but primarily Allen Bradley and GE and find the productivity series as or more intuitive to program than those but if you have experience with a different platforms do-more or click might be easier to learn.

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Thanks again for all your input.
I'm just a lowly maintenance manager/ plant manager. even our electromechanics are proficient with the discreet controllers that control 90% of our plant, and have some little experience with allen bradley (mostly just what they learned in school little practical activity). we use 2 or 3 lovato PLC's in small applications, and we have 1 koyo DL05 we are using in a silo level application, that I somehow managed to cobble together many years ago (still chooches fine...). we even have a pretty sophisticated opacity level meter/controller that runs on an arduino/ nexion HMI.
so I'm up for some learning, hopefully with some help here and there.

The budget for the project is probably 2500$-3000$ for parts, so I assume that if I stick to automationDirect parts I should be fine. what is more important is that system is stable, reliable, simple... the old durant controller literally only required the controller and some wires. I don't love having to set up an hmi, but I think that might be simpler than a keypad, 3 lines of lcd characters, 3-4 switches, power supplies, we might even ru out of space in the panel. an hmi seems more elegant, and even if more expensive probably less time consuming to set up, particularly since if this works well on 1 line we willreplicate the system for 5 or 6 production lines (am I wrong on that?).

I'll start looking more into depth and reading the BRX manual, I'm sure I'll have even more questions about hmi choice, etc.
thanks again,
Alex

Thats all still less than half your budget.
You could do a ton more than a simple count with that too. Such as email you daily production counts, or make a 2 stage control where when it gets close to your cut length it slows down to a slower speed to "creep" the rest of the way for a more precise cut
With leftover budget money you could look at using it to make a better motor system as well like maybe with a big stepper and gearbox or maybe even a 400w-1kw servo (depending on torque needed for the size of your plastic) so that the BRX could even tell it exact pulses to move to get perfect lengths each time with the encoder used for closed loop feedback control. Even a servo system with this PLC stuff would still fit within the $3000 for parts you mentioned.